1. Field of the Invention
The present invention relates to a method for placing plastic tubes into existing openings and through-passages, particularly into buried tube shaped through-passages or into existing pipe lines which have to be renovated, as well as to an apparatus for carrying out the method.
2. Description of the Prior Art
An actual technique for lining through-passages or openings in the ground with a plastic tube or to renovate existing pipe lines of various diameters by means of tubular plastic inserts consists in that such plastic tubes are placed in said openings or through-passages by either pulling or pushing the tubes into the desired position. In a particularly suitable process the plastic tube to be placed in such a through-passage is produced in situ, e.g. the tube is manufactured by a known winding process starting from plastic band material. The winding machine necessary for such a procedure is very often placed in the shaft or manhole on the hight or level of the through-passage. The plastic tube is wound up by said machine (winding cylinder) and simultaneously fed into said through-passage.
Independently of the technique of manufacturing said plastic tube and of inserting it into the through-passages, the tube should not be too stiff or rigid, this at least for the case where it has to be introduced into a through-passage which does not follow a straight line. It is practically impossible to insert and particularly to insert by pushing a tube into a curved through-passage except when using tubes of relatively flexible material and furthermore pulling the tubes into the through-passage. However, such tubes have often the disadvantage, once in the desired position, to have a stiffness which is fully insufficient in view of the loads appearing at such locations.
Attempts have been made to obviate this disadvantage by complicated mechanical devices (spring tensioning mechanism). However, the result was not very encouraging compared with the very high costs.